Retrieves, but does not remove, the head row of this result set,
waiting up to the specified wait time if necessary for a row to become
available, or returns END_OF_RESULTS if there are no more rows in this
result set.

Retrieves, but does not remove, the head row of this result set,
returns null if there is no row currently available in this result
set, or returns END_OF_RESULTS if there are no more rows in this
result set.

Retrieves and removes the head row of this result set,
waiting up to the specified wait time if necessary for a row to become
available, or returns END_OF_RESULTS if there are no more rows in this
result set.